Bird Naps: How Migratory Flyers Catch Up on Sleep

We humans have trouble functioning when we are sleep-deprived, but some birds accomplish great migratory feats with little nighttime sleep. They may make up for the sleep they lose flying at night by snoozing—sometimes resting only half their brain for seconds at a time—while perched during the day. Studying these “micro-naps” may yield clues about how to combat human ailments related to sleep deprivation.

By examining EEG recordings, scientists recently con­firmed that captive Swainson’s thrushes fall asleep almost immediately and nap for five to 10 seconds during periods of drowsiness. In some instances, the birds keep one eye open in a semialert state, possibly to watch for predators, while the other eye rests and the corresponding half of their brain sleeps. Other birds and a few aquatic mammals (which must periodically swim to the sur­face to breathe) also experience “unihemi­spheric” sleep.

It is hard to imagine humans taking one-eyed naps, says one of the study’s authors, Verner Bingman, a behavioral neuroscientist at Bowling Green State University. Our brains are much more intercon­nected than those of a bird, which has hemispheres that can work more independently, he explains. Nevertheless, birds might teach us about how humans could compensate for sleep deprivation. It is not yet clear if the birds make up for all their sleep lost during the migratory season, according to Ruth Benca, a psychiatrist who studies animal sleep at the University of Wisconsin–Madison. If, instead, their need for sleep changes throughout the year, studies such as this one could help us to better understand insomnia and other human disorders, she says.

Note: This article was originally printed with the title, "Napping Is for the Birds".

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